Ultratherm UTH's are very high quality, but a store brand (Zoo-Med, Exo Terra, etc.) are fine as well. The key is to get a good thermostat to regulate the UTH's temperature, and a probed thermometer to monitor the cage temps. Thermostats are NOT optional. Without a thermostat nearly all UTH's will get hot enough to burn/give brain damage to your snake (130 F +)
Keep in mind that UTH's do very little if anything for air temps in the cage, they only heat surfaces they are in direct contact with (heat transfer via conduction)
Here are some good thermostats:
Budget: http://www.amazon.com/Hydrofarm-MTPR.../dp/B000NZZG3S
Mid-Range: http://www.reptilebasics.com/thermos...stat-prewired/
Best: http://www.spyderrobotics.com/home/products.html
Here is a good probed thermometer:
http://www.walmart.com/ip/Acu-Rite-I...ndingMethod=rr
More info: http://ball-pythons.net/forums/showt...t-Thermometers